Conventionally, a vehicle, such as a two-wheel vehicle or a four-wheel car, includes a clutch device which is disposed between a prime mover such as an engine and a driven body such as a wheel. The clutch device transfers rotational drive force from the prime mover to the driven body and interrupts the transfer. In general, a clutch device includes friction plates which are rotated by rotational drive force of a prime mover and clutch plates connected to a driven body. Each of the friction plates faces a corresponding one of the clutch plates. Transfer of rotational drive force and interruption of the transfer can be performed at will by bringing the friction plates and the clutch plates into a tightly coupled state or a separated state.
The friction plates and the clutch plates are brought into the tightly coupled state by pressing a pressure plate against a friction plate or clutch plate. For example, below-listed Patent Document 1 discloses a clutch device in which coil springs are disposed in concave receiving portions of a pressure plate with spring seats disposed therebetween, and the pressure plate is pressed against a friction plate by means of elastic forces of the coil springs.